It has long been known that UV radiation has a germicidal effect and that the naturally occurring UV radiation in sunlight has a disinfecting effect at a sufficient intensity and duration. For the disinfection of water and wastewater, UV radiation is used in small and large plants, see for example patent specification U.S. Pat. No. 1,150,117, which is incorporated by reference herein. Therein a distinction can be made between plants in which UV lamps are arranged in closed channels and such plants in which the UV lamps are arranged in channels that are upwardly open, so-called gutters. The second design with open gutters is used predominately in wastewater technology. The clarified wastewater is therein led through an open channel to the UV plant and there is subjected to UV radiation in order to reduce the number of germs to such an extent that the clarified wastewater can, for example, be introduced into bodies of water. The disinfection power can therein be so high that the introduction into bathing water is admissible.
Wastewater treatment plants are normally constructed such that the water flows from an inlet, through various treatment steps, to an outlet, solely due to gravity, without pumps being required. Therefore it is also aimed, in UV treatment plants in wastewater technology, to keep the flow resistance as low as possible in order to achieve a likewise low pressure loss in the provided flow rate. Such a pressure loss is expressed, during the operation of the plant, in a height difference between the water level in the inlet and the water level in the outlet. It is aimed to keep this height difference as low as possible.
Because of the particularly favourable electrical efficiency, so-called mercury low pressure lamps are predominantly used for the water disinfection, which have an elongated lamp tube made from quartz in which a gas discharge between two electrodes generates the UV radiation. The length of such a lamp amounts to approx. 1.5 m. The lamps are inserted into cladding tubes made from quartz in a watertight manner, for protection against water and for maintenance of the operating temperature, said cladding tubes then in turn being arranged in the water to be disinfected. This assembly of UV lamp and cladding tube is subsequently referred to as a lamp.
Commercial plants, such as, for example, those used in the procedure of communal clarification plants, normally have a plurality of lamps, sometimes over 100 pieces.
In the case of plants having an open channel, also called a “gutter”, there are various arrangements of the lamps. The lamps can lie horizontally and in parallel to the flow direction in the channel (see, for example, patent specification U.S. Pat. No. 4,482,809, which is incorporated by reference herein, and U.S. Pat. No. 6,500,312, which is incorporated by reference herein). The lamps can also lie horizontally and transversely to the flow direction, see patent specification U.S. Pat. No. 4,367,410, which is incorporated by reference herein. Finally, there are plants in which the lamps stand or hang vertically in the channel, for example in patent specifications U.S. Pat. No. 5,660,719, which is incorporated by reference herein, and U.S. Pat. No. 5,332,388, which is incorporated by reference herein.
Several UV lamps are combined into modules. These modules must be lifted from the channel for maintenance purposes in order, for example, to exchange individual lamps or to clean the lamp surface. Smaller modules having, for example, four to eight lamps can be lifted manually out of the channel. Larger modules require the use of a crane. Alternatively, modules can also be mounted to be able to pivot at one end (upstream or downstream), such as is shown, for example, in US patent application US 2008/0260602 A1, which is incorporated by reference herein. A module can then be pivoted upwards out of the channel. In the case of the patent application referred to, for this purpose a handle is provided, which enables the manual pivoting of the module. In the case of larger modules, it is also known to provide a rotary actuator, which pivots the module upwards out of the channel.
In particular for larger modules, which, for example, can have more than twenty lamps, the lifting-out with a crane is disadvantageous, because, on the one hand, a heavy hanging load must be moved, and on the other hand, in the case of vertically mounted lamps, an open position results in the channel, which is very deep and represents a fall hazard for personnel. Both circumstances represent a potential risk of accidents. In the case of modules which are provided with a rotary actuator, a free space is required in the channel due to the pivoting movement in the flow direction, which corresponds to the total length of the module. For this purpose, it is in turn required to keep the channel free for this length. A correspondingly long zone results in which a fall hazard can result for the personnel. The modules that have been pivoted upwards are situated, in the pivoted-out state, above the channel, which must be covered accordingly in order to be able to service the individual lamps. This is also seen as a disadvantage in practice.